Abstract
Ellipsometric measurements have been made of optical properties of the heavy rare earth metals Gd, Tb, Dy, Ho, Er in the phonon energy range 0.35 eV to 2.5 eV and at certain temperatures between 20K and 300K corresponding to various magnetic phases of the metals. Rather diversive optical behaviour of the metals below the ordering temperature is interpreted in terms of exchange splitting of the levels near the Fermi level causing their reoccupation.